1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a medium for extracting characteristics of an object to be measured included in a photographed image.
2. Description of the Related Art
In the case where color reproduction characteristics of a device are measured, there is a method of performing measurement by displaying or outputting a patch for each color one by one by using the device. For example, there is a method of sequentially measuring images based on RGB data (729 (=9×9×9) colors in total) obtained by slicing the ranges of R, G, and B between 0 and 255 (0≦R, G, B≦255) into nine ranges, respectively, as patches. However, this method requires a number of measurement processes because measurement is performed for each color, and as a result, requires a long time in order to measure the color reproduction characteristics of one device.
Further, there is a method of displaying or outputting charts including all the color reproduction ranges of a device and measuring the charts at a time by using a two-dimensional measuring instrument such as a digital camera. Furthermore, a method of automatically measuring charts has been proposed. Japanese Patent Laid-Open No. 2008-278054 has proposed a method of extracting a chart area by analyzing color information along a plurality of directions perpendicular to one another in an image acquired by measuring a chart including an already-known background color using a two-dimensional measuring instrument.
Japanese Patent Laid-Open No. 2008-278054 premises that the patches included in the chart image acquired by using a two-dimensional measuring instrument are arranged along two directions perpendicular to each other. Because of this, the case where it is possible to accurately detect the chart area is limited to the case where the chart image can be acquired by using a two-dimensional measuring instrument in a position substantially facing the chart.
In the case where the two-dimensional measuring instrument does not face the chart perfectly, a distortion occurs in the chart in the image acquired by measurement. In the case where the extraction range of the patch is set uniquely in the chart having a distortion, there is a possibility that the extraction range will not fit inside the patch. In this case, it is not possible to extract the characteristics of the patch with accuracy, and as a result, there occurs such a problem that it is not possible to acquire the color characteristics of a device with high accuracy.